1. Field of the Invention
The present invention relates to a wiper system.
2. Description of Related Art
For example, Japanese Utility Model Publication No. H07-39734 discloses a roof spoiler (a wiper system), which includes a wiper mechanism that wipes a surface of a rear window glass of a vehicle. The above roof spoiler is installed to a top end portion of the back door panel or a rear end portion of a roof panel and receives the wiper mechanism that wipes the rear window glass.
Furthermore, Japanese Unexamined Patent Publication No. 2002-370626 discloses another technique. According to the disclosed technique, a recess, which is recessed inward of a vehicle, is provided in a top portion of a back door panel of the vehicle, and a rear wiper motor apparatus is installed in this recess. Upon installation of the rear wiper motor apparatus in the recess, an outer panel (a rear spoiler) is installed.
FIG. 11 is a descriptive view of a previously proposed wiper system, which should be only considered as an illustrative comparative example for illustrating advantages of the present invention. As shown in FIG. 11, the previously proposed wiper system includes an accommodation space 120a, which is formed in a spoiler 110 to accommodate a wiper arm 133 and a wiper blade 134.
In the previously proposed wiper system, the wiper blade 134 is accommodated in the accommodation space 120a of the spoiler 110 when the wiper blade 134 is placed in a stop position thereof. Thus, for example, at the time of snowfall, the snow, which is wiped by the wiper blade 134, is wiped into the accommodation space 120a and is accumulated therein.
Normally, a wiping surface area size of the wiper blade 134 is increased from a pivot axis side 134b of the wiper blade 134 to a distal end side 134a of the wiper blade 134 in conformity with an increase in a length of an arcuate wiping path of the wiper blade 134 along the length of the wiper blade 134. Thus, the amount of snow, which is wiped by the wiper blade 134 at the time of snowfall is larger at the distal end side 134a in comparison to the pivot axis side 134b. Therefore, one longitudinal side of the accommodation space 120a, which accommodates the distal end side 134a, tends to accumulate the larger amount of snow in comparison to the other longitudinal side of the accommodation space 120a, which accommodates the pivot axis side 134b. 
However, in the previously proposed wiper system, a depth of the accommodation space 120a is made generally constant along the length of the accommodation space 120a regardless of the location along the length of the wiper blade 134. Specifically, as shown in FIG. 11, a distance S1 between the distal end side 134a of the wiper blade 134 and a depth end wall 122a is generally the same as a distance S2 between the pivot axis side 134b and the depth end wall 122a. 
Thus, while the other longitudinal side of the accommodation space 120a, which accommodates the pivot axis side 134b of the wiper blade 134, may have a sufficient space for accumulating the wiped objects (e.g., snow), the one longitudinal side of the accommodation space 120a, which accommodates the distal end side 134a of the wiper blade 134, may not have sufficient space for accommodating the wiped objects. When the accommodation space 120a accumulates the large amount of the wiped objects, the distal end side 134a of the wiper blade 134 tends to be caught by the wiped objects, and thereby causing a damage to the wiper blade 134 or locking of the wiper motor apparatus upon continuation of the wiping operation due to the capturing of the wiper blade 134 in the wiped objects.